The present invention relates to a method and a device for controlling an exhaust gas aftertreatment system, for example, an exhaust gas aftertreatment system of an internal combustion engine.
A method and a device for controlling an internal combustion engine having an exhaust gas aftertreatment system are described, for example, in German Published Patent Application No. 199 06 287, in which an exhaust gas aftertreatment system includes a particle filter used, for example, in direct injection internal combustion engine. The loading of the particle filter is detected as a state quantity. When specific values are exceeded, the device initiates a special operating state, in which suitable measures regenerate the particle filter.
The differential pressure, i.e., the pressure difference between the inlet and the outlet of the filter, may be evaluated to detect the load state. When the particle filter is damaged, for example, if the particle filter is torn, the load state of the filter may not be reliably detected via the differential pressure, since a portion of the exhaust gas may flow through the tear. In addition, particles may be emitted into the environment, which may result in violation of emission standards.
In accordance with an exemplary embodiment of the present invention, the exhaust gas aftertreatment system may be easily and reliably monitored by determining a second quantity, based on second characteristic operating quantities characterizing an amount of substances removed from the exhaust gas aftertreatment system in a second operating state, in which the particle filter is regenerated, and by comparing this second quantity to the first quantity characterizing an amount of substances supplied to the exhaust gas aftertreatment system. Errors may be detected when the two quantities significantly deviate from one another.
An exemplary method according to the present invention may be used in conjunction with particle filters, the amount of particles accumulating in the particle filter during normal operation being compared to the amount of particles combusted during regeneration.
It is believed that the amount of substances removed may be simply and reliably determined by evaluating the temperature upstream and downstream from the particle filter. During regeneration of the particle filter, the reaction of the particles results in a temperature increase, which may be detected using sensors upstream and downstream from the particle filter. A defect in the filter may be reliably detected based on the comparison of these two quantities.
The second quantity may include, for example, a signal characterizing the amount of oxygen in the exhaust gas. To this end, the oxygen content in the exhaust gas upstream and downstream from the filter may be detected. A conclusion as to the amount of regenerated particles may be made based on the mass of the reacted oxygen.